Perhaps you mean to press Alt+Tab, which is the Windows Task Switcher.
Also, you can enhance that with the free Microsoft Powertoy called "Alt-Tab Replacement" available at:
i am using topdesk and it works on my computer...which is a 1 gig , 80 gig harddrive win XP only 10 months old....when i presss win + tab it will put my screen in flip 3d mode but there is only one window..no matter i f i have 10 tabs open nothing..help. i have firefox 188.8.131.52 and i have the open new pages in a new window box checked but this doesnt work. how do you get like 2 or 3 or 5 windows up so i can flip between many windows and not just one? help me please...